This study seeks to address two pressing scientific needs: 1) to improve ways to sample and recruit hard-to-reach minority populations for inclusion in research and 2) to fill a gap in our knowledge of the health problems faced by female-to-male transgender persons (transmen). Minority populations unduly suffer from many diseases and mental health conditions; sexual minorities bear a particularly heavy burden of the HIV epidemic. We are seeing warning signs that transmen may be an overlooked minority population at high risk for HIV, with documented AIDS and STD cases, sex partners who are gay men and male-to-female transgender persons (transwomen) and low condom use. Transmen also appear to face discrimination and have high levels of drug and alcohol use, depression and suicide. However, reliable data are lacking to guide prevention and care programs. This exploratory study will develop and test a novel strategy to sample and recruit transmen for a survey of HIV prevalence and health risks, beginning with outreach to public places where transmen are found followed by referral of their peers. Although this study focuses on transmen, our research will invent and validate a new sampling method applicable to diverse populations affected by HIV and other health issues worldwide.